Different methods are used to follow the microbial populations during beer fermentation and maturation. In recent years biomolecular methods, based on the use of PCR, have been developed to study the fate of implicated microorganisms in beer fermentation. These methods allow for the evaluation of yeast during the fermentation phase, and the bacteria or yeasts responsible for the beer alteration. Brewing yeasts characterization and contaminant bacteria identification using fast molecular methods such as PCR, RAPD-PCR, PCR-TGGE, PCR_DGGE, short tandem repeats (STR) analyses are now important tools to improve beer quality. This chapter explains the main biomolecular methods developed and optimized to identify brewing yeasts and bacteria by culture-dependent and culture-independent methods.
